The much-anticipated ceremony kicks off at 12pm sharp and there'll be plenty of people - royal-watchers and star-gazers alike - getting up at the crack of dawn to watch the proceedings unfold.
Prince Harry and Meghan Markle's nuptials will be more low-key than Prince William and Kate Middleton's. The Duke and Duchess of Cambridge's wedding was held in Westminster Abbey and deemed worthy of an official British bank holiday.
There'll be considerably less pomp and ceremony during Harry and Meghan's big day, but make no mistake, there will be no less interest.
According to a recent poll by Amarách Research for RTÉ's Claire Byrne Live, just over a third of Irish people said they'll be paying attention to the Royal wedding, while 57pc said that they would not. How the participants of this particular poll define 'paying attention' is another question entirely. Granted, Irish people won't be hanging bunting or standing, hand over heart, for 'God Save The Queen'. They will, however, be paying attention to this wedding on some level.
While some will unashamedly lap up every last detail, many more will watch the wedding in the spirit of perfunctory duty or guilty pleasure. Like it or not, there's a silent majority who don't want to confess their interest in the British monarchy, or their better-than-average knowledge of its complicated lineage.
Royal weddings are a little like Eurovision in this regard. Nobody admits to enjoying the high camp flight of fancy but come the moment, they can't get enough of it.
When we hear the terms 'royalist' or 'royal-watcher', we tend to think of an ageing population of Britons who buy Union Jack waistcoats and commemorative tea clothes, and who camp outside the lido with flasks of tea.
We don't think of the hundreds of Irish people who left flowers at the British Embassy when Princess Diana died, the vast numbers who tune into the Queen's Christmas Day speech or the lavishness of the green carpet welcome that we extended to her majesty in 2011.
Royal weddings are captivating, and even the most committed anti-monarchists will find it difficult to disengage from the soap opera around this latest one.
Meghan's father has been caught staging paparazzi photographs while her half-brother has been kept busy sending poison pen letters. It's like a stunt Dana White might orchestrate to boost PPV numbers, or a scene a Suits writer might pen for a series finale.
While some of us will tune in tomorrow for the royal romance and the Gok Wan fashion commentary, many more will tune in for the family drama and the denouement of a TMZ celebrity gossip rollercoaster.
This is Prince Harry, after all: the royal who dressed up as a Nazi for a fancy dress party; the royal who was photographed naked during a stag do in Las Vegas. He's the royal that even anti-royalists like, so his wedding will probably attract more attention than his older brother's nuptials in 2011.
There'll be street parties and picnics galore in Britain tomorrow. The celebrations will be rather more subdued in Ireland, although there are a few specially organised afternoon teas taking place in hotels like The House in Galway and Dunboyne Castle in Meath. West Brits might even wear a cocktail hat and gloves for the occasion, but there's always the risk of running into someone from work...
Closet royal-watchers will be conducting their secret love affair with the British Royal Family from the safety of their sitting rooms. They might up the ante with Pimms cocktails, celebratory bubbles and cucumber sandwiches (crusts off, plebeians). As for the incredulous '800 years of oppression!' family member who keeps interrupting Philip Schofield's commentary? Just remind him that he'll be parked in front of the TV for the FA Cup Final later in the day...
It wouldn't be a royal wedding party without some party games. You could play royal wedding bingo: down a drink every time the commentator compares Meghan's dress to her sister-in-law's, or describes the bride as 'stunning'. Otherwise, there are plenty of betting opportunities to keep you interested. Donald Trump is currently 500/1 with Paddy Power to walk Meghan down the aisle. You could also get your hands on the deliciously cringey Harry & Meghan: A Royal Romance. The movie takes artistic licence with its portrayal of Harry (Murray Fraser) and Meghan's (Parisa Fitz-Henley) relationship as the Meghan character seduces the prince with the line: "I've always had a thing for redheads."
Otherwise, just stay in your pyjamas, ensconce yourself on the couch and look out for these key moments...
William and Kate's guests included the Beckhams, Guy Ritchie and, er, Joss Stone. The A-list guest list provided some much-needed razzle-dazzle, but it was hardly Met Ball stuff. Harry and Meghan, on the other hand, will bring out the big guns with an invite list that is said to include the Clooneys, the Spice Girls (all five of them) and Dave Grohl (left) of the Foo Fighters.
The royal wave
The royal wave is a subtle art that Meghan has, so far, failed to master. She either looks like a beauty pageant contestant or a visiting guru when she raises her arm. She'll have had plenty of practice before her big reveal tomorrow, and we'll be looking forward to seeing what kind of wave she extends to her fans.
Beatrice & Eugenie
It wouldn't be a royal wedding without an appearance from Beatrice and Eugenie, the Royal Family's very own Patsy and Eddie. The sisters are known for their absolutely fabulous fashion choices and we can't wait to see their latest interpretation of appropriate headwear.
The surprise performance
William and Kate surprised their guests with a performance by the reassuringly vanilla Ellie Goulding. Harry and Meghan know we expect much more from them. Stormzy would be a touch too much but Ed Sheeran is probably hiding in a wardrobe at Windsor Castle right now, ready to jump out and shout 'Boo!'.
Meghan's ex-husband hasn't been invited to the wedding but it is rumoured that two of Harry's exes, Cressida Bonas and Chelsy Davy, have made the cut. We know where we'll be looking when Harry says 'I do'.
The African influence
You only have to look at Prince Harry's trademark beaded bracelets to know he has a grá for all things Africa. Couple this with the fact that he fell in love with Meghan under the stars in Botswana and it's safe to conclude that there'll be some sort of African theme to the proceedings. Ladysmith Black Mambazo are playing in Suffolk tonight. Just saying...